The present disclosure relates more specifically to a high-temperature friction adjustment interface inserted between two parts made of nickel or made of nickel alloy or made of cobalt-chromium alloy that are in relative motion against one another. This interface makes it possible to reduce the surface wear of the two parts due to the friction between the two parts at high temperature, namely between the temperatures of 300° C. and 650° C. in an oxygen-containing atmosphere. This interface is particularly suitable for the parts used in applications that require particular tribological properties.
Nickel alloys such as for example Inconel 718 (registered trademark) have properties that are highly desired in the aeronautical industry, due to their mechanical strength at high temperature and their resistance to oxidation at high temperature.
However, nickel alloys have very poor friction behavior, associated with a marked tendency for galling, and a high sensitivity to the effect of scratching, and their use is particularly limited for applications that require particular tribological properties at high temperature.
In the aeronautical industry, the articulation joints that function at high temperature between the motor and pylon components are provided by an assembly constituted of ball joint, axle and rings. The parts constituting this system may be produced by nickel alloys such as Inconel 718.
This ball joint system generally comprises a concave part and a spherical part borne by an axle. The spherical part that is housed in the concave part is driven by a rotational movement in all directions; the surface of the spherical part and the surface of the concave part are in permanent friction against one another.
A distinction is mainly made, in the case of the ball joint system and in other similar systems, of two types of frictional wear, wear by very low amplitude friction which is generally of the order of a few micrometers to a few tenths of millimeters, also known as fretting wear or else vibratory frictional wear under load and additionally sliding wear, the amplitude of movement of which reaches several tens of millimeters. Frictional wear develops from fine asperities present on the rubbing surfaces in contact and that tend to stick together. When the load applied locally is high and in the case where the materials of the rubbing surfaces have similar compositions, the frictions give rise to surface wear and degradations that may range up to the galling of the axle or of the ball joint. These wear phenomena are even higher when these parts are made of nickel alloy. Furthermore, the high temperature of the environment (between 300° C. and 650° C.) favors the appearance of adhesive wear ultimately responsible for the galling cases.
It is therefore desirable to carry out a surface treatment of the parts made of nickel or nickel alloy or cobalt-chromium alloy for systems that are subject to continuous friction.
Commonly owned French patent application publication FR 2 907 468, filed 20 Oct. 2006, relates to a low-temperature adjustment interface. Described in this patent is a coating based on WC-C:H obtained by a physical vapor deposition (PVD) process combined with a copper alloy coating obtained by thermal spraying. This coating is satisfactory at a temperature below 250° C. On the other hand, these pairs of interface materials may prove less effective or even ineffective above a certain temperature since the copper is converted to copper monoxide and the WC-C:H graphitizes: therefore, the articulation wears rapidly and this type of interface leads to a rapid galling for very high temperatures between 400° C. and 650° C.